Functional aerogels composed of regenerated cellulose and tungsten oxide were fabricated by implanting tungsten-oxide nanodots into regenerated cellulose fiber. This superfast photochromic property benefitted from the small size and even distribution of tungsten oxide, which was caused by the confinement effect of the regenerated cellulose fiber. The composite was characterized using XRD and TEM to illustrate the successful loading of tungsten oxide. The composite turned from pale white to bright blue under ambient solar irradiation in five seconds. The evidence of solar absorption and electron paramagnetic resonance (EPR) demonstrated the fast photochromic nature of the composite and its mechanism. Furthermore, carbon fiber filled with preferential growth tungsten-oxide nanorods was obtained by annealing the photochromic composite in a N2 atmosphere. This annealed product exhibited good absorption across the whole solar spectrum and revealed an excellent photothermal conversion performance. The water evaporation rate reached 1.75 kg m−2 h−1 under one sun illumination, which is 4.4 times higher than that of pure water. The photothermal conversion efficiency was 85%, which shows its potential application prospects in seawater desalination.
